Preterm uterine contractions or insufficient contractile activity during labor result either in miscarriage or in emergency cesarean section. A proper understanding of the mechanisms of uterine contraction and its cellular regulation is essential in finding ways to treat these uterine functional pathologies. Although, the mechanisms of uterine smooth muscle contraction are generally understood, the factors responsible for the initiation of labor and the mechanisms by which the uterus maintains its contractility during labor are largely unknown. A growing body of evidence suggests that protein kinase C (PKC) plays an important role in regulation of contraction in a number of smooth muscles. However, its role in regulation of myometrium (uterine smooth muscle) is still controversial. Experimental results show both stimulatory and inhibitory effects of PKC on myometrial contraction. This complex mode of PKC action on myometrium can be explained by diversity within the PKC family of proteins, consisting of 12 known isoenzymes (isoforms). We recently showed that 7 of the isoforms are expressed in human non-pregnant myometrium, while in late pregnancy two more, PKCB1 and PKCB11are expressed. We have also shown a progressive increase in PKCa expression during pregnancy. We hypothesize that different isoforms of PKC play specific stimulatory or inhibitory, roles in regulating contraction of human myometrium. Early in the contraction-relaxation cycle some PKC isoforms can stimulate contractile pathways, and later other isoforms can decrease the rate of contraction, thus contributing to the muscle relaxation. Firstly, individual PKC isoforms will be depleted in myometrial cell line and muscle strips of human pregnant myometrium using isoform-specific anti-sense oligodeoxynucleotides (ODN). Secondly, the impact of this procedure on the intracellular free Ca concentration in the cell line and on the intracellular free Ca and the contraction of the muscle strip will be elucidated by measuring these parameters in the cells and the muscle strip. Knowing a crucial role of intracellular Ca ([Ca 2+]l)in uterine contraction, the effect of the PKC depletion on [Ca2+] l / force relationship will be analyzed. This will help us to better understand how PKC affects the uterine contraction during pregnancy. Within the scope of this application we'll concentrate on elucidation of the role(s) of PKCa and B as the isoforms expressed differently in pregnancy. [unreadable] [unreadable]